You might need to go into your bios and select the primary graphics adapter as the radeon instead of the IGPU (intel). If so, it would be found in the "advanced" tab in the bios usually.
You can also try going into device manager (right click the start menu onwindows 10, and select device manager). Go to the display adapters section, and try disabling the intel gpu. Also check in the radeon settings (in device manager) that windows is not allowed to turn off the radeon to save power. If you are not plugged in, it might turn off the readeon so you don't drain your battery, even though you are trying to use it to game. Dumb, I know.
Let us know how those fixes work out.